Dynamical DMRG study of spin and charge excitations in the four-leg t-t'-J ladder

TL;DR

This study uses dynamical DMRG to analyze how stripe order affects spin and charge excitations in a four-leg t-t'-J ladder, revealing doping-dependent behaviors similar to experimental observations in cuprates.

Contribution

It provides a detailed dynamical analysis of stripe effects on excitations in a four-leg t-t'-J ladder, connecting theoretical results with experimental findings.

Findings

Stripe order causes low-energy charge excitations in hole doping.

Incommensurate spin excitations form an hourglass shape in hole doping.

Spin-wave-like dispersions are observed in electron doping.

Abstract

The ground state of the t-t'-J ladder with four legs favors a striped charge distribution for the parameters corresponding to hole-doped cuprate superconductors. We investigate the dynamical spin and charge structure factors of the model by using the dynamical density matrix renormalization group (DMRG) and clarify the influence of the stripe on the structure factors. The dynamical charge structure factor along the momentum direction from q=(0,0) to (pi,0) clearly shows low-energy excitations corresponding to the stripe order in hole doping. On the other hand, the stripe order weakens in electron doping, resulting in fewer low-energy excitations in the charge channel. In the spin channel, we find incommensurate spin excitations near q=(pi,pi) forming an hourglass behavior in hole doping, while in electron doping we find clearly spin-wave-like dispersions starting from q=(pi,pi). Along the (0,0)-(pi,0) direction, the spin excitations are strongly influenced by the stripes in hole doping, resulting in two branches that form a discontinuous behavior in the dispersion. In contrast, the electron-doped systems show a downward shift in energy toward (pi,0). These behaviors along the (0,0)-(pi,0) direction are qualitatively similar to momentum-dependent spin excitations recently observed by resonant inelastic x-ray scattering experiments in hole- and electron-doped cuprate superconductors.